What worries me is that there might be some electrical difference... can I just drop a CMOS CPU into a socket formerly occupied by an NMOS version? Most ZX Spectrums will run okay with a 6 or 8MHz CMOS Z80. I don’t know if anyone has tried a 10MHz or a 20MHz rated CMOS Z80. The reason for the cavea...

The CPU that is fitted, if an original part, will be a NMOS type rated at4MHz. NOTE there are versions by manufacturers other than Zilog. Zilog’s orginal part number for the 4MHz version was simply Z80A CPU. Any CMOS version should work. However, there is no advantage in buying one with a higher spe...

The keyboard is actually the same as the ZX Spectrum+, which is an evolution of the rubber key using “technology” developed for the Sinclair QL. The layout was set before the PC keyboard became common in this country. If you look at the various keyboards on home machines available between 1979 and 1...

One document you should read through if you are using BASIC, is the 16k/48k manual. Here is an easy to read version.
As well as explaining BASIC, it also does cover the basics of the machines architecture, such as the reading of the keyboard, the screen, the memory map etc...

To be fair, the 128k BASIC editor is rubbish. In some ways, I prefer the 16k/48k editor, minius the keyword entry system (assuming you are either using an Amstrad machine, a decent third party keyboard, or a emulator on a PC witch a decent keyboard).

Yes, the coil is actually vibrating at the frequency generated by transistors TR4 and TR5. This is normal for coils in issue 1 and issue 2 machines. Sinclair used better made coils in later machines that make less noise and also revised the circuit design a number of times. But they still often make...

Velesoft has his own website and posts on the forums at World of Spectrum . The most likely place would be in the hardware sub-forum here . The WoS forums are not scanned by search engines, so will not show up any results in a search engine. The DIVMMC is an evolution of earlier DivIDE interfaces, w...

The key legends on the original Spectrum are also set in Helvetica, by the way, not Arial. Keep that in mind. Aww c'mon—nitpicking. To the layperson, these fonts are all the same: http://stonechatproductions.co.uk/zxgames/gameimages/ZXFonts.png I don’t know. That last one looks a little off. Can’t ...

I see you have already removed some of the components from your board. For the benefit of others, I will still list the components that need removing. ZX Spectrum, Issue 3 board, suppling from an external regulated PSU Remove the following components from the ZX Spectrum PCB: REG - 7805 voltage regu...